JP7408998B2 - Inkjet printer and inkjet printer driving method - Google Patents

Description

The present invention relates to an inkjet printer and an inkjet printer driving method.

In an inkjet printer, a cable connects a drive board for the inkjet head and the inkjet head, and the ejection of ink from the inkjet head is controlled by a head drive signal from the drive board.

In order to improve the quality of printed images by printers, it is preferable to make the length of the cable connecting the drive board and the inkjet head as short as possible. By shortening the cable length, it is possible to prevent the print quality from deteriorating due to waveform distortion or rounding of the head drive signal.
On the other hand, the applications of inkjet printers are expanding, and various larger inkjet printers are being developed. In the case of large-sized inkjet printers, it is often structurally difficult to shorten the distance between the drive board and the inkjet head.

Patent Document 1 discloses that in order to shorten the cable between the drive board and the head in a printer, everything from a digital-to-analog converter (DA converter) to a drive waveform output circuit is placed on a child board separate from the drive board, and the child Techniques are described for placing the substrate close to the head.

Japanese Patent Application Publication No. 2018-158494

As described in Patent Document 1, it has been conventionally known to provide a slave board to shorten the length of a cable connecting the slave board and the head. However, if everything from a DA (digital/analog) converter to a drive waveform output circuit is arranged on a slave board, it is necessary to transmit digital data for driving the head from the drive board to the slave board. For example, it is necessary to transmit multiple bits (for example, 12 bits) of data to the slave board for each head. The number of bits of this drive data tends to increase as the quality of printed images becomes higher.

Assuming an inkjet printer with 12-bit drive data and 5 drive circuits per head, 60 cables (12 x 5 cables) are used to connect the drive board and slave board for each head. Need to connect. In this way, when a large number of cables are prepared to connect the drive board and the slave board, the configuration of the drive system of the inkjet printer becomes considerably complicated. Specifically, it is necessary to route many cables for a long time, which increases the cost required for the cables, and also requires a space to route a large number of wiring cables inside the printer, which is not preferable.

An object of the present invention is to provide an inkjet printer and an inkjet printer driving method that can prevent deterioration of print quality with a simple configuration.

The inkjet printer of the present invention includes a drive waveform generation unit that generates a drive waveform for an inkjet head, a converter that converts digital data of the drive waveform generated by the drive waveform generation unit into an analog waveform voltage, and an analog waveform voltage converted by the converter. A control board has a drive waveform voltage amplification circuit that amplifies the waveform voltage to a voltage level that drives the inkjet head, and an analog waveform voltage output from the drive waveform voltage amplification circuit of the control board is supplied, and the analog waveform voltage is The present invention includes a drive substrate having a drive waveform power amplification circuit for amplifying power to a level capable of driving the elements of the inkjet head, and an image data buffer circuit disposed on the drive substrate for controlling the inkjet head.
Then, the analog waveform voltage power amplified by the drive waveform power amplification circuit of the drive board is supplied to the inkjet head , and the image data supplied to the buffer circuit is a differential signal, and the drive board receives the differential signal. It is equipped with a differential receiver .

Furthermore, in the inkjet printer driving method of the present invention, in which an analog waveform voltage for driving an inkjet head is supplied to the inkjet head, digital data of a driving waveform generated in a control board is converted into an analog waveform voltage. After amplifying the converted analog waveform voltage to the voltage level that drives the inkjet head, it is transmitted from the control board to the drive board via a cable, and within the drive board, the transmitted analog waveform voltage is amplified to the voltage level that drives the inkjet head. The power is amplified to a level that can drive the element , and a buffer circuit placed on the drive board buffers the image data that controls the inkjet head. The image data that is supplied to the inkjet head and also to the buffer circuit is a differential signal .

According to the present invention, even if the distance from the control board to the inkjet head is long, by installing the drive board close to the inkjet head, it is possible to prevent distortion and rounding of the drive waveform, thereby reducing deterioration in print quality. can be effectively prevented.

FIG. 1 is a block diagram showing an overall example of an inkjet printer according to an embodiment of the present invention. FIG. 1 is a block diagram of main parts of an inkjet printer according to an embodiment of the present invention. 1 is a configuration diagram showing an example of connection of a board of an inkjet printer according to an embodiment of the present invention. FIG. 1 is a circuit diagram of an inkjet printer according to an embodiment of the present invention (an example in which a negative feedback circuit is provided on a drive board); FIG. FIG. 3 is a diagram showing an example of a driving waveform of an inkjet printer according to an embodiment of the present invention. FIG. 3 is a block diagram of main parts of an inkjet printer according to another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An inkjet printer according to an embodiment of the present invention (hereinafter referred to as "this example") will be described below with reference to FIGS. 1 to 5.

[Overall configuration of inkjet printer]
FIG. 1 is a block diagram showing the overall configuration of an inkjet printer 1 of this example.
The inkjet printer 1 includes a control section 50 , a movement control section 21 , a movement operation section 61 , a communication section 62 , a head drive control section 10 , an inkjet head 40 , and the like, which transmit signals via a bus 63 . Connected for sending and receiving.

The control unit 50 centrally controls the overall operation of the inkjet printer 1. The control unit 50 includes a CPU (Central Processing Unit) 51, a RAM (Random Access Memory) 52, a storage unit 53, and the like.
The CPU 51 performs various calculation processes. The CPU 51 reads out a control program stored in the storage unit 53 and performs various control processes related to image recording, its settings, and the like.
The RAM 52 provides a work area for the CPU 51 and stores data being worked on.

The storage unit 53 includes a nonvolatile memory that stores control programs, setting data, and the like. Further, the storage unit 53 includes a DRAM and the like that temporarily stores settings related to the print job, image data to be recorded, etc. acquired from the outside via the communication unit 62.
The moving operation unit 61 moves the recording medium on which an image is to be recorded in a predetermined direction, thereby moving the recording medium relative to the inkjet head 40, and at least performs operations related to supplying and discharging the recording medium. I do. Examples of the moving unit 61 include a rotary motor that rotates around the outer periphery of a cylindrical drum that carries a recording medium on its surface, or the surface of an endless belt.

The movement control unit 21 operates the movement operation unit 61 to perform a control operation to move the supported recording medium at appropriate timing and speed. This movement control section 21 may have a common configuration with the control section 50.

The inkjet head 40 is provided with a plurality of nozzles arranged in a predetermined pattern, and records an image on a recording medium by ejecting ink droplets from the openings of the plurality of nozzles at appropriate timing. The inkjet head 40 includes a piezoelectric element 41 that is a capacitive load, and a drive control section 42 that includes an ejection selection switching element and the like.

The piezoelectric element 41 is provided for each of the plurality of nozzles, and deforms according to the applied voltage (driving voltage waveform) to change the pressure applied to the liquid to be ejected, thereby ejecting droplets from the nozzle. It is an actuator. The piezoelectric element deforms in accordance with the voltage value of the drive voltage.

The drive control section 42 switches whether or not to supply a drive voltage signal from the head drive control section 10 to each piezoelectric element. The drive control unit 42 switches whether or not ink droplets are ejected from each nozzle by not supplying a drive voltage waveform to the piezoelectric elements 41 corresponding to the nozzles that are not allowed to eject droplets based on the image data to be output or the like.
Note that this switching by the drive control unit 42 is performed not only when ejecting ink droplets, but also when supplying a non-ejection waveform with a small amplitude to the extent that no ink droplets are ejected.

The head drive control unit 10 outputs a drive voltage signal that drives the piezoelectric element 41 of the inkjet head 40 at appropriate timing according to each pixel data of the output target image. The head drive control section 10 is formed on a control board 10a. Other circuits such as the control section 50 may be arranged on the control board 10a.

The head drive control section 10 includes a drive waveform generation section 11 , a digital-to-analog converter (hereinafter referred to as "DAC") 12 , and a drive waveform voltage amplification circuit 13 .
The drive waveform generation section 11 includes a CPU 11a and a storage section 11b, and the digital data of the drive waveform stored in the storage section 11b is read out under the control of the CPU 11a.

The digital data of the drive waveform output from the drive waveform generator 11 is converted into an analog drive waveform voltage by the DAC 12 . The analog drive waveform voltage converted by the DAC 12 is amplified by the drive waveform voltage amplification circuit 13 to a voltage level that drives the inkjet head 40 .

The drive waveform voltage amplified by the drive waveform voltage amplification circuit 13 is output from the control board 10a and supplied to the drive waveform power amplification circuit 31 arranged on the drive board 30. The control board 10a and the drive board 30 are connected by a cable 71 (FIG. 3). This drive board 30 is installed at a location relatively close to the inkjet head 40 within the inkjet printer 1.
The drive waveform power amplification circuit 31 amplifies the power of the supplied analog waveform voltage to a level that can drive the piezoelectric element 41 of the inkjet head 40 .
The drive waveform voltage power amplified by the drive waveform power amplification circuit 31 of the drive board 30 is supplied to the piezoelectric element 41 of the inkjet head 40 . The drive board 30 and the inkjet head 40 are connected by a cable 72 (FIG. 3).

[Configuration in which driving waveform is supplied to the inkjet head]
FIG. 2 shows a configuration in which a drive waveform is supplied from the control board 10a to the inkjet head 40 via the drive board 30.
Drive waveform data generated by the drive waveform generator 11 of the control board 10a is converted into an analog drive waveform voltage by the DAC 12 in the control board 10a. The drive waveform voltage converted by the DAC 12 is supplied to the drive waveform voltage amplification circuit 13 in the control board 10a, and is amplified to a voltage level that drives the inkjet head 40.

The drive waveform voltage amplified by the drive waveform voltage amplification circuit 13 is transmitted from the control board 10a to the drive board 30, and is power amplified by the drive waveform power amplification circuit 31 in the drive board 30 to a level capable of driving the piezoelectric element 41. be done.
The drive waveform voltage power amplified by the drive waveform power amplification circuit 31 is supplied to the piezoelectric element 41 of the inkjet head 40 . The piezoelectric element 41 is driven by this drive waveform voltage. That is, the piezoelectric element 41 deforms in response to the voltage of the drive waveform, changing the pressure applied to the liquid to be ejected.

FIG. 3 shows how the control board 10a, drive board 30, and inkjet head 40 are connected.
The control board 10a and the drive board 30 are connected by a cable 71. A drive waveform voltage amplified by the drive waveform voltage amplification circuit 13 is transmitted to this cable 71 .
The drive board 30 and the inkjet head 40 are connected by a cable 72. A drive waveform voltage whose power has been amplified by the drive waveform power amplification circuit 31 is transmitted to this cable 72 .

Note that the control board 10a is installed at a location where the entire printer operation is controlled together with a board on which the control unit 50 and the like are arranged. On the other hand, the drive board 30 is placed near the inkjet head 40. Therefore, the cable 72 connecting the drive board 30 and the inkjet head 40 is shorter than the cable 71 connecting the control board 10a and the drive board 30. For example, the cable 71 has a length of about several tens of centimeters to several meters, whereas the cable 72 has a length of about 10 centimeters. Note that since only limited circuits such as the drive waveform power amplification circuit 31 are disposed on the drive board 30, it can be configured with a circuit board having a small area.
By configuring the drive board 30 with a small-area circuit board, the drive board 30 can be placed near the inkjet head 40, and the length of the cable 72 can be shortened.

[Circuit configuration]
FIG. 4 shows an example of the circuit configuration of the drive waveform voltage amplification circuit 13 of the control board 10a and the drive waveform power amplification circuit 31 of the drive board 30. Note that FIG. 4 shows an example in which a negative feedback circuit 32 is provided before the drive waveform power amplification circuit 31. This negative feedback circuit 32 is also arranged on the drive board 30. However, providing the negative feedback circuit 32 before the drive waveform power amplification circuit 31 is just one example, and a configuration without the negative feedback circuit 32 may also be used.

The drive waveform voltage amplification circuit 13 includes an operational amplifier U1 and resistors R1 and R2. The output of the DAC 12, which is the previous stage circuit, is supplied to the non-inverting input terminal (+) of the operational amplifier U1. Then, a resistor R1 is connected between the output terminal of the operational amplifier U1 and the inverting input terminal (-), the inverting input terminal (-) is grounded via the resistor R2, and a voltage is amplified from the output terminal of the operational amplifier U1. The generated drive waveform is output.

The drive waveform voltage output from the drive waveform voltage amplification circuit 13 is supplied to the negative feedback circuit 32 of the drive board 30. Negative feedback circuit 32 is composed of operational amplifier U2 and resistors R3 and R4. The output of the drive waveform voltage amplification circuit 13, which is the previous stage circuit, is supplied to the non-inverting input terminal (+) of the operational amplifier U2. The output of the drive waveform power amplification circuit 31 is supplied to the inverting input terminal (-) of the operational amplifier U2 via a resistor R3. Further, a resistor R4 is connected between the output terminal of the operational amplifier U2 and the inverting input terminal (-). The output end of the operational amplifier U2 is connected to the drive waveform power amplification circuit 31.

The drive waveform power amplification circuit 31 is composed of field effect transistors M1 and M2. Field effect transistor M1 is an N-channel field effect transistor, and field effect transistor M2 is a P-channel field effect transistor.
The output of the negative feedback circuit 32 (the output of the operational amplifier U2) is supplied to the gates of the two field effect transistors M1 and M2. A power supply VCC is supplied to the drain of the field effect transistor M1, and a drain of the field effect transistor M2 is grounded. Then, the sources of the two field effect transistors M1 and M2 are connected, and the signal obtained at the connection point of the sources of the two field effect transistors M1 and M2 is used as the output of the drive waveform power amplification circuit 31. The output of this drive waveform power amplification circuit 31 is supplied to the piezoelectric element 41 of the inkjet head 40.
Note that in FIG. 4, the voltage amplification circuit 13 and the negative feedback circuit 32 are shown close to each other, but in reality, as explained in FIG. A feedback circuit 32 is connected thereto.

[Example of drive waveform voltage]
FIG. 5 shows an example of the drive waveform voltage supplied to the piezoelectric element 41.
FIG. 5(a) shows the drive waveform voltage Va supplied to the piezoelectric element 41 in the case of the configuration of this example explained in FIGS. 2 to 4.
In the case of the configuration of this example, the drive waveform voltage Va is power amplified by the drive waveform power amplification circuit 31 disposed immediately before being supplied to the piezoelectric element 41, so the waveform at the time of being supplied to the piezoelectric element 41 is There is almost no distortion or accent. Therefore, the piezoelectric element 41 of the inkjet head 40 can be driven appropriately, and factors that degrade the quality of printed images by the inkjet head 40 can be eliminated, resulting in higher image quality.

For comparison, FIG. 5(b) shows the drive waveform voltage Vb when the drive waveform power amplification circuit 31 is provided on the control board 10a.
In this case, the drive waveform voltage Vb is power amplified and then transmitted through a relatively long cable and supplied to the piezoelectric element 41, so that distortions X1, X2, etc. occur in a part of the waveform. When the piezoelectric element 41 is driven with such a drive waveform voltage Vb, image quality deteriorates corresponding to the distortions X1 and X2.

As explained above, according to the inkjet printer 1 of this example, even when the distance from the control board 10a to the inkjet head 40 is relatively long, it is possible to supply an appropriate drive waveform voltage to the piezoelectric element 41 of the inkjet head 40. This can prevent deterioration of print quality.

[Example of combining the drive board with other circuits]
Note that other circuits may be arranged on the drive board 30.
The example in FIG. 6 shows an example in which a buffer circuit 33 for image data supplied from the control board 10a to the drive control unit 42 of the inkjet head 40 is arranged on the drive board 30. The image data supplied to the drive control section 42 via the buffer circuit 33 is digital data.
The other configuration of the example in FIG. 6 is the same as the example in FIG. 2.

Note that when the buffer circuit 33 is arranged as shown in FIG. 6, in order to prevent mutual interference between the drive waveform voltage on the drive waveform power amplification circuit 31 side and the image data, the cable for image data transmission is the cable 71, Preferably, it is separate from 72 (FIG. 3).
Furthermore, if the image data is a differential signal, the drive board 30 may include a differential receiver.

[Other variations]
Note that the present invention is not limited to the embodiments described above, and modifications and changes can be made without departing from the gist of the present invention.
For example, the overall configuration of the inkjet printer 1 shown in FIG. 1 is one example, and the present invention may be applied to inkjet printers with other configurations.
In addition, FIGS. 2, 4, etc. show a configuration for supplying a drive waveform voltage to one inkjet head 40, and when a plurality of inkjet heads 40 are arranged, a plurality of drive waveform voltages are provided on the drive board 30. A drive waveform power amplification circuit 31 is arranged.
Further, the circuit configuration shown in FIG. 4 is also shown as an example, and the present invention is not limited to the configuration shown in FIG. 4. The provision of the negative feedback circuit 32 as shown in FIG. 4 is also a preferable example, and a configuration in which the negative feedback circuit 32 is not provided may also be used.

DESCRIPTION OF SYMBOLS 1... Inkjet printer, 10... Head drive control part, 10a... Control board, 11... Drive waveform generation part, 12... Digital-to-analog converter (DAC), 13... Drive waveform voltage amplification circuit, 30... Drive board, 31... Drive Waveform power amplification circuit, 32... Negative feedback circuit, 33... Buffer IC, 40... Inkjet head, 41... Piezoelectric element, 42... Drive control unit

Claims (5)

a drive waveform generation unit that generates a drive waveform for the inkjet head;
a converter that converts the digital data of the drive waveform generated by the drive waveform generator into an analog waveform voltage;
a control board having a drive waveform voltage amplification circuit that amplifies the analog waveform voltage converted by the converter to a voltage level for driving the inkjet head;
a drive board having a drive waveform power amplification circuit that is supplied with the analog waveform voltage output from the drive waveform voltage amplification circuit of the control board and amplifies the power of the analog waveform voltage to a level that can drive the elements of the inkjet head;
an image data buffer circuit disposed on the drive board and controlling the inkjet head;
The analog waveform voltage power amplified by the drive waveform power amplification circuit of the drive board is supplied to the inkjet head, and the image data supplied to the buffer circuit is a differential signal, and the drive board Equipped with a differential receiver that receives dynamic signals
inkjet printer. The inkjet printer according to claim 1, wherein a cable connecting the drive board and the inkjet head is shorter than a cable connecting the control board and the drive board. The inkjet printer according to claim 1, wherein the drive board includes a negative feedback circuit that corrects the analog waveform voltage by applying negative feedback to the output of the drive waveform power amplification circuit. The inkjet printer according to claim 1, wherein the drive board includes a drive waveform power amplification circuit for a plurality of the inkjet heads. An inkjet printer driving method for supplying an analog signal waveform for driving an inkjet head to the inkjet head,
The drive waveform digital data generated within the control board is converted into an analog waveform voltage, and the converted analog waveform voltage is amplified to a voltage level that drives the inkjet head, and then is driven from the control board via a cable. transmit to the board,
A circuit arranged on the drive board amplifies the power of the transmitted analog waveform voltage to a level capable of driving the elements of the inkjet head,
buffering image data for controlling the inkjet head with a buffer circuit disposed on the drive board;
The analog waveform voltage power amplified by a circuit disposed on the drive board is supplied to the inkjet head via a cable , and the image data supplied to the buffer circuit is a differential signal.
How to drive an inkjet printer.

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